NSFetchedResultsController错过合并的NSManagedObjectContext的更新 [英] NSFetchedResultsController misses updates on merged NSManagedObjectContext

问题描述

我有两个管理对象上下文A和B.这两个上下文保持同步，通过将更改从一个保存到另一个保存（通过监视 NSManagedObjectContextDidSaveNotification ）。我已验证对A和B的更改正确合并。

I have two managed object contexts, A and B. These two contexts are kept in sync by merging changes from one to the other whenever they're saved (by monitoring NSManagedObjectContextDidSaveNotification). I've verified that changes to A and B are merging properly.

我有一个 NSFetchedResultsController 监视B的更新。我发现对A的某些更新不会导致nsfrc在B上创建一个新的管理对象并添加到A中，并使用nsfrc正在查找的属性（在B上），则在B合并A的保存更改之后触发nsfrc。但是，如果受管对象已经存在A（和B），并且我修改对象并保存A，同时我可以看到B正在合并来自A的保存通知的更改，nsfrc监视B不会触发。

I have an NSFetchedResultsController monitoring updates to B. I find that certain updates to A do not result in the nsfrc firing on B. When a new managed object is created and added to A with the attributes the nsfrc is looking for (on B), the nsfrc fires after B merges changes from the save of A. However, if the managed object already exists on A (and B), and I modify the object and save A, while I can see that B is merging the changes from the save notification of A, the nsfrc monitoring B does not fire.

我在这里缺少什么？

推荐答案

我有这个问题，似乎我已经解决了。我不知道我做了什么。我的意思是我做了几件事情，不知道，哪一个成为解决方案。所以我将简单描述...

I had this problem and it seems that I've solved it. I don't know what I did exactly. I mean I did a couple of things and don't know, which one became the solution. So I will simply describe...

我重构了我的代码以跟随一些提示，发现在官方文档&一些论坛：

I've refactored my code to follow some "hints", found in official docs & some forums:

1. 如果你在另一个线程中管理 NSManagedObjectContext


2. 您应该在主线程中添加observer（以获取合并的保存通知） - 这样它们也将合并到主线程中。
   
3. （可选，但我做到了）你可以尝试在主线程中保存上下文，即使它是在后台线程中创建和管理的。

1& 3看起来更像一些魔法，所以我想你应该尝试按照2先。希望这将帮助你。

1 & 3 looks more like some "magic", so I think you should try to follow 2 first. Hope this will help you.

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